Dielectric heating system having provision for selection of preset electrode spacings



June 27, 1950 A. PROCTOR EI'AL 2,512,751

nmuzcmxc HEATING SYSTEM HAVING PROVISION FOR SELECTION OF PRESETELECTRODE SPACINGS Filed Aug. 1, 1946 5 Sheets-Sheet l Fig.1..

INVENTORS Ausf/n Proafor Harold A. Kusferer A T TORNEKS June 27, 1950OCTOR HAL 2,512,751

A. PR DIELECTRIC HEATING SYSTEM HAVING PROVISION FOR SELECTION OF PRESETELECTRODE SPACINGS 5 Sheets-Sheet 2 Filed Aug. 1, 1946 l/MMfM A T TORNEKS June 27, 1950 A. PROCTOR ETAL 2,512,751

DIELECTRIC HEATING SYSTEM HAVING PROVISION FOR SELECTION OF PRESETELECTRODE SPACINGS Flled Aug 1, 1946 5 Sheets-Sheet 3 lNVE/VTORSx4057??? Frocfor Miro/d A/(us/ref WWW/WM ATTORNEYS June 27, 1950 A.PROCTOR ETAL 2,512,751

DIELECTRIC HEATING SYSTEM HAVING PROVISION FOR smzcnon 0F PRESETELECTRODE SPACINGS 5 Sheets-Sheet 4 Filed Aug. 1, 1946 I/NVE/VTORSAusT/n Procf'o f/aro/d A. lfusferer ATTORNEYS June 27, 1950 A. PROCTORETAL 2,512,751

DIELECTRIC HEATING SYSTEM HAVING PROVISION FOR SELECTION OF PRESETELECTRODE SPACINGS A /sflh fiwcfor flaw M A. flusfsrer ATTGR/VEYSPatented June 27, 1950 DIELECTRIC HEATING SYSTEM HAVING PROVISION FORSELECTION OF PRE- SET ELECTRODE SPACINGS Austin Proctor, Louisville,Ky., and Harold A. Kusterer, Richmond, Va., assignors to The GirdlerCorporation, Louisville, Ky., a corporation of Delaware ApplicationAugust 1, 1946, Serial No. 687,786

6 Claims.

This invention relates to dielectric heating systems and particularly toa dielectric heating unit whose alternate or successive loads mayrequire different spacing of the heating electrodes and differentheating periods.

In accordance with the invention, there is provided a control member,preferably operable from the exterior of the unit, to vary the electrodespacing and whose positions corresponding with predetermined spacingssuited to different loads are predetermined by stops preferablyadjustable 'from the exterior of the unit. More specifically,

to adapt the unit for heating of different loads alternately deliveredto two molding presses, the stops for the control member are adjusted incorrespondence with predetermined minimum and maximum electrode spacingssuited respectively to the different loads of the two presses, so thatthe operator after heating and removal of one load need only shift thecontrol member to its other position to obtain proper electrode spacingfor the next load.

Further in accordance with the invention, switches included in timingcircuits, or in pressindicating circuits, or both, are adjustableconcurrently with the stops for selective actuation by the controlmember upon its movement to the different load positions.

The invention further resides in features of combination, construction,and arrangement hereinafter described and claimed.

For a more detailed understanding of my invention and for illustrationof a preferred embodiment thereof, reference is made to the acccmpanyingdrawings, in which:

Fig. l, in perspective, shows the heating unit with the load traypartially withdrawn;

Fig. 2 is a detailed view, in p an, showing the control member and stopsfor determining the electrode spacing;

Fig. 3, in side elevation, shows parts appearing in Fig. 2;

Fig. 4, in perspective, and in part an exploded view, shows theoperating mechanism for the movable electrode;

Fig. 5 is a detailed view, on enlarged scale, showing a latchconstruction; and

Fig. 6 is a simplified wiring diagram of the power supply and controlcircuits included in the heating unit.

Referring to Fig. 1, the heating unit It! comprises a high-frequencygenerator for applying a hi h-frequency voltage to an upper movableelectrode 13 disposed within the unit and to a lower electrode I2forming the bottom of a load tray 2 II which may be inserted into andwithdrawn from the unit through the opening 11 in the front wall orpanel thereof. The channel guides 9, which slidably receive the oppositeedges of the tray to ensure proper positioning of the lower electrode l2are aligned with the opening ll. Heating units of this type are commonlyused for heating preforms of dielectric material which, after beingheated to temperature at which they are suitably soft, are removed fromthe heating unit and transferred to a molding press. The same heatingunit is often used to heat preforms of different dimensions for deliveryto different presses and one of the purposes of the present invention isto provide arrangements so that the operator may, once certainadjustments hereinafter described are made, quickly adapt the unit forproper rates and periods of heating of alternate loads deliveredrespectively to two presses.

For example, when the control member or operating handle l8 projectingfrom the front of the panel of the unit is thrown to the left, thespacing between the electrodes I2 and I3 is suited for heating ofpreforms of a certain height, the spacing being determined by thepresetting of the adjustable stop ll extending through the front of thepanel. The corresponding timer l4, preset to deenergize thehigh-frequency generator after a predetermined time suited to the load,is set by the operator to its start position. With the loaded tray inits inserted position, the operator then presses the start" button l9and the heating period begins. As hereinafter appears, the movement ofthe control member I6 to the lefthand position also actuates a switchcontrolling the left press indicator lamp 2|, or equivalent, so thatduring the heating period the operator is constantly informed that theload in the furnace is for the left press and that so long as theindicator lamp 2| is lighted the heating period is as yet incompleted.When the indicator goes out at the end of the heating period, theposition of the control member I6 is again a reminder to the operatorthat the load in the heater is for the left" press.

After the load for the left" press is removed from the tray I l, thecontrol member 16 is thrown to the right to position determined by thepreset adjustable stop i8 extending through the front of the panel, soto change the spacing between electrodes l2 and I3 to one suited for thepreforms to be heated for the right press. After the tray is loaded andpushed into the heating unit, the operator sets the "right press timer,not shown in Fig. l, to the "start position and then presses the rightpress starting button 20. Until the heating period is completed, the

indicator lamp 22 continues to inform the opera- From the foregoing, itappears that once the stops I1 and I8, and the two timers, have beenadjusted to suit two different types of loads, the operator thereaftermay quickly adapt the unit for heating of the different loads bythrowing the control member I6 from one to the other of its positions.

The preferred operating mechanism between the control member I6 and theupper electrode I3 is more fully shown in Figs. 2-4 inclusive. Thecontrol handle I6 is mounted on or forms the front end of the rod 23which extends through the slot 15, Fig. 1, in the front panel of theheating unit. The inner end of rod 23, Figs. 2-4, is

fastened by the nut 24 to the bent end of an arm 25 pivotally mountedfor angular movement in a horizontal plane upon the lower end of thecolumn 21 supported at its upper end by plate 28 which extends betweenthe cross members 30 at the top of the unit and secured to them by thebolts 29.

The arm 25 is secured to or formed integrally with the cross-arm 26extending at right angles thereto and through the opposite ends of whichvertically extend the pivot pins 3| and 32, either of which may beselected to couple the control member I6 to link 34. In Fig. 2 the link34 is shown connected to the left end of cross-arm 26 by pin 3| and isretained in position by the spring clip 33 or equivalent. With the linkso connected, movement of handle I6 to the left raises the electrode I3,as will hereinafter appear, whereas if link 34 is coupled to theright-hand end of arm 26, Fig. 2, by the coupling pin 32, handle I6 ismoved to the right to raise the electrode l3. This provision is topermit the heating unit conveniently to be used regardless of which ofthe two presses requires the greater spacing of the heating electrodesand to preserve the relations above described between the leftandright-hand indicators, the timers, and the control handle positions.

The rear end of the link 34 is pivotally connected by pin to the yokemember 35 pivotally mounted in the up er end of arm 36 secured to ashaft 31 supported at its opposite ends by bearin s 36 at the lower endof member 54, Fig. 3. which is secured by bolts I 05 to the verticalframe members I06 of the heating unit. The pin 43, Figs. 2 and 4, of theyoke 35 extends through the upper end of arm 36 and the yoke is retainedin place by the nut 44 which threadably engages the projecting end ofpin 43.

The pair of arms 39 secured to shaft 31 extend forwardly therefrom andare pivotally connected at their forward ends by the pins 4| to the L-shaped brackets 40, Fig. 4, the nuts 42 holding the pins in place. Thebases of the brackets are held by bolts 41 and nuts 46 to theelectrodesupporting plate 45. To the upper ends of brackets 46 arepivotally connected, as by pins '43, a pair of rearwardly extending arms48 secured, as by wedge pins, to shaft 52 which extends across the unitand whose opposite ends are received by the bearing members 53, Fig. 2,which at the upper end of member 54 are secured, as above described, tothe frame members 4 I66 of the unit. The counterbalance 55, Figs. 3 and4, is attached by bolts 56 to, and extends between, the rear extensionsof arms 48. The pivot pins 43, Fig. 2, for the forward ends of the arms46 are held in place as by nuts 50 or equivalent.

The three insulators 51 for supporting the upper electrode I3 are eachprovided with a mounting member 59 secured to the under face of theplate 45 by screws 58. Similarly, the lower end of each insulator isprovided with a mounting member 60 fastened as by bolts H to th'. upperface of the electrode I3.

The arms 39, 48 and brackets 40 provide a panallel-motion linkage sothat as the control member I6 is moved to the right or left, theelectrode I3 is raised and lowered with its lower face remainingparallel to the tray electrode I2 below it so insuring uniformity of thepotential gradient between the opposed surfaces of the electrodes.

Upon the rod or bar 23 of the control member is slidably mounted a block63 from which'depends a pin 82 which is received by the opening or bore63 in the carriage 64 slidable upon the guide rod 65. The guide rod 65is mounted immediately behind and parallel to the front panel of theheating unit by the brackets 66 through which the ends of the rodextend, the nut 61 threadably engaging the ends of the rod to secure itto the brackets. Brackets 66 are held by bolts 62 to the cross framemember I08. The stop members 69 respectively to the left and right ofthe carriage 64 are bored to slide along the guide rod 65 and areslotted axially of the bore so that they may be tightened to hold themin desired position.

As most clearly appears in Fig. 4, the left" stop 69, to the right ofthe drawing, is threaded to receive the threaded rear end of theadjustable stop member I! which extends through the slot I5 in the frontof the panel. By turning a wrench in engagement with the external end ofthe member II, the left stop 69 may be loosened and slid along member 65by pushing against the external portion of member I'I. When the stop hasthus been adjusted to position corresponding with the desired spacing ofthe electrodes I 2 and I 3, the member I! may be tightened to squeezetogether the two portions of the slotted member 69 and so clamp itsecurely in its adjusted position or guide bar 65. The right stop membermay be similarly adjusted by stop member or bolt I6, Fig. 2, to providea different desired spacing of the electrodes I2 and I3. Both theseadjustments can, as described, be effected without need for access tothe interior of the unit.

The end of each stop member 69 engaged by the carriage or slide 64 isprovided on its under surface with a recess I0, Fig. 5, for reception ofa ball latch II resiliently mounted in a corresponding extension I2 ofthe carriage. As clearly shown in Fig. 5, the ball II is resilientlybiased by a spring I3, interposed between the ball II and the plug 14,to project above the upper face of the carriage extension I2. The upperend of the bore which receives the ball is of reduced diameter to retainthe ball. As the carriage is moved toward or from the position indicatedin Fig. 5, the ball is forced downwardly by engagement with the lowerface of the stop extension and so does not impede operation of handleI6. When, however, the carriage is in either of its stop-limited posi-'tions, the corresponding ball Ii moves upwardly into the recess Iii ofthe corresponding stop in ell-cot to latch the handle in position and sopreaura-m a switch I8 which is closed when the control member I is movedto it "left press position. For operation of the switch 18, the carriage84 is provided with a housing 80 secured to the left extension 8| of thecarriage and from which extends a resiliently mounted plunger I01.Similarly, upon the right" press stop 89 is mounted a switch 19 likewiseactuated by a resiliently mounted plunger I01 extending from the housing89 on the right end of the carriage 84, as viewed looking toward theouter end of handle it, Fig. 2.

Thus, when the position of either of the externally adjustable stopmembers l1 and I8 is changed to predetermine the electrode spacings, thecorresponding switch 18 or 19 i concurrently adjusted for operation bythe operating handle or member It as it is moved to its right or leftposition. The purposes of the switches 18 and 19 will appear from thefollowing discussion of Fig. 6.

The high-frequency generator housed in the unit I8 is preferably aself-excited oscillator, comprising thermionic tube 85, having a broadlytuned grid circuit including the inductor 89. The direct-current gridvoltage is derived from the usual resistance-capacity network formed byresistor 81 and capacitor 88. The direct-current voltage of the anode'ofthe tube is supplied by the source 95 whose high-voltage positiveterminal 99 is connected to the anode through the radio-frequencychoke-coil 89. The negative terminal 9| of the high-voltage circuit isconnected to the cathode of the tube as by the ground or chassisconnections indicated. The anode of the tube is connected, forhigh-frequency currents, through a blocking capacitor 92 to a tankcircuit including the inductor 99 and a capacitor formed by the heatingelectrodes l2 and I3.-The connections from the inductor 99 to the anodeand to the upper electrode l3 may be variable for impedance-matching andtuning purposes. The low-voltage supply terminals 94 of the power supply95, which may be the conventional step-up transformer, rectifier andfilter arrangement, are connected to the supply-circuit conductors I99adapted to be connected through the contacts 96F to the line conductors99 extending to a suitable source of alternating current.

The supply conductors Hill are also connected to the branch lineconductors IOI extending to control circuit components disposed withinthe housing ill of the unit. When the load tray I2 is in proper heatingposition, it effects closure of a switch 84 to connect one of the branchconductors "H to the control circuit conductor I82 common to all of thecontrol circuit component: hereinafter discussed and including the"start switches 19 and 28, the indicators 2| and 22, the timer motors l4and I5, the timer motor contacts HT and I5T, the relays 91, 98 and theircontacts, and the coil of the contactor 95 whose contacts 96F controlconnection of the power supp y and of the control system components tothe line conductors 99.

Unless the tray switch 84 is' closed, none of the relay or timercircuits can be completed by closure of either of the start buttons l9or 28. Assuming the tray 84 is in position and that the handle it hasbeen -thrown to the right for heating of preforms for the "right pressand the various contacts of the control circuits are in 6 the conditionshown in Fig. 6: it should be noted that the right press switch 19 isclosed and the "left" press switch 18 is open. Should the improp r stopbutton, the "left press button l9,

he accidentally closed, nothing happens because this branch of thecontrol circuit is interrupted by the open switch 18 which is closedonly when the control handle I8 is in the left position. The failure ofthe indicator 2| to light, upon closure of button l9, indicates to theoperator that he has made a mistake but provision of switch I8 insuresthat such mistake is of no consequence.

When the proper start button 28 is momentarily pressed, a circuit iscompleted through the back contact 91B of relay 91, the -start" switch29, the coil of relay 98, the selected press switch l9 and the contactsl'5T of the timer l5 which has been set to start position beforedepression of the switch 29. The energization of relay 98 effectsmovement of its forward contacts 98F to complete a seal-in or holdingcircuit about the push button 20 which, as above stated, is onlymomentarily depressed. The energizntion of relay 98 also efiectsenergization, through its main contacts 98M, of the contactor coil 95whose contacts 96F thereupon close to effect energization of the powersupply 95, thus to initiate application of high-frequency voltage to theload on the tray l2. Concurrently with energization of relay 98 there isalso completed a circuit through the right" press timing motor l5 sothat at the end of the preset time interval, the timer contact HT isopened to effect de-energization of relay 98 with consequentinterruption of the circuit of contactor coil 96 and de-energization ofthe high-frequency generator by the resulting opening of the contacts96F. Throughout the period of energization of relay 98, the left pressindicator 2% is energized, preferably through the current-limitingresistor I94, to indicate to the operator that a load for the right-handpress is being heated.

Smilarly, when the control member or handle It has been thrown to theleft to adjust the electrode spacing to suit a load for the left pressand to effect closure of the switch 19, and assuming that the load trayhas been inserted into the unit to effect closure of the tray switch 84,the "start" button 19 is momentarily depressed to initiate heating ofthe load for a period determined by the setting of the timer M. Therelay 91 controls a seal-in or holding circuit including its contacts91F and also controls the main contactor 96 through its main contacts97M. At the end of the preset heating interval, the timer contact l4Topens the branch control circuit for the left press and so de-energizesthe relay 9'! with consequent de-energization of the contactor 99 andde-energization of the power supply 95 by opening of the line contacts96F of relay 98. During this period the left press indicator 9| isenergized, preferably through the current-limiting resistor I03.

As appears from the foregoing, once the stops I1 and I8 and the timershave been set in accordance with the different load requirements of thetwo presses, the operator need only throw the control handle it to theright or left and press the proper starting button in order to insurethat the proper voltage is applied to each load and for a properinterval of time. It is thus insured that the heating unit may be usedwith maximum economy of time and also without serious consequence if theoperator should inad- 7 vertently fail fully to insert the load tray orto press the proper start" button.

It shall be understood the invention is not limited to the particulararrangement disclosed but that modifications and changes may be made,all, however, within the scope of the appended claims.

What is claimed is:

1. A dielectric heating system comprising spaced electrodes and suitedfor heating successive loads alternately requiring two differentoperating spacings of said electrodes, structure supporting saidelectrodes for relative movement with their opposing faces inparallelism, an actuating member for said structure movable in oppositedirections respectively to increase and decrease the spacing betweensaid electrodes, and preadjustable abutments respectively engaged bysaid actuating member upon movement thereof in said opposite directionsalternately to position said supporting structure for operation of saidparallel electrodes alternately with said two different spacings.

2. A dielectric heating system comprising spaced electrodes and suitedfor dielectrically heating successive loads alternately requiringdiii'erent operating spacings of said electrodes, means operable to varythe spacing between said electrodes including a member manually movablein opposite directions respectively to increase and decrease the spacingbetween said electrodes, stops for limiting the movement of said memberin opposite directions in predetermination of the minimum and maximumspacings of said electrodes respectively suited for the known alternateloads, and a pivoted reversing link included in said means andselectively connected to one or another pivot point to predeterminewhich of said opposite directions of movement of said member increasesthe electrode spacing and which decreases it.

3. A dielectric heating system comprising a removable load tray forminga lower electrode, an upper electrode parallel to said lower electrode,and means for raising and lowering said upper electrode including anoperating member movable horizontally in opposite directionsrespectively to raise and lower said upper electrode, means to translatehorizontal movement of said member to vertical movement of said upperelectrode and to maintain parallelism of said electrodes, and stopstructure adjustable to define the limits of movement of said member insaid opposite directions in predetermination of proper spacing of saidelectrodes respectively for two different types of load.

4. A dielectric heating system comprising a lower electrode, avertically movable upper electrode, operating means for said upperelectrode including a parallel-motion linkage and a manually operablemember movable in one direction to raise said upper electrode to aposition of maximum electrode-spacing and in reverse direction to lowersaid upper electrode to a position of minimum electrode-spacing, and amotion-reversing connection between said member and said parallel-motionlinkage for interchanging the said positions of said membercorresponding respectively with the raised and lowered positions of saidupper electrode.

5. A dielectric heating unit comprising a loadtray removable through awall of said unit, an electrode, structure for supporting said electrodein parallelism with said tray and actuatable for vertical movement ofsaid electrode toward and ."from said tray in a path clear of the pathof said tray, and an actuating lever connected to said structure andextending through said wall for movement externally of the unit inopposite directions respectively to positions corresponding with twooperating positions of said electrode suited for two differenttray-loads.

6. A dielectric heating unit comprising spaced electrodes and suited forheating successive loads alternately requiring two different operatingspacings of said electrodes and two diiferent periods of application ofradio-frequency voltage, structure supporting said electrodes forrelative motion of their opposing faces in parallelism, timing devicespreset to afiord said difierent periods of voltage application, switchesfor selective energization of said timing devices, and an actuatingmember mechanically connected to said structure and selectively engagingsaid switches operable in opposite directions repeatedly alternately toprovide said operating spacings of the electrodes and concurrently toprovide the corresponding periods of application of radiofrequencyvoltage thereto.

AUSTIN PROCTOR. HAROLD A. KUSTERER.

REFERENCES CITED The following references are of record in th file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,876,106 Usselman Sept. 6, 19322,442,451 Albin June 1, 1948 OTHER REFERENCES Plastics Engineering,March 1943, page 90.

Modern Plastics, June 1944, page 118.

Thcrmex Catalogue for Model 2P Thermex, August 1944.

Gilbert, Automatic Tuning System for Preheating Plastics, Electronics,December 1944, page 116.

Product Engineering, August 1945, page 526.

Certificate of Correction Patent No. 2,512,751 June 27 1950 AUSTINPROGTOR ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Column 4,line 20, after the Word and period electrodes. insert As evident fromthe drawings, the loaded tray may be removed from the heating unitwithout obstruction by the upper electrode or any of its actuatinglinkage; column 5, line 75, for circuits read circuit;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the ease in the PatentOffice.

Signed and sealed this 24th day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Gammissioner of Patents.

Certificate of Correction Patent No. 2,512,751 June 27 1950 AUSTINPROCTOR ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

, Column 4, line 20, after the Word and period electrodes. insert Asevident from the drawings, the loaded tray may be removed from theheating unit without obstruction by the upper electrode or any of itsactuating linkage; column 5, line 75, for circuits read circuit;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOflice.

Signed and sealed this 24th day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

